netdev - Re:Re: [PATCH] Fix MRU mismatch issue which may lead to data connection lost

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Date:   Sat, 15 Jan 2022 10:10:40 +0800 (CST)
From:   "Slark Xiao" <slark_xiao@....com>
To:     "Loic Poulain" <loic.poulain@...aro.org>
Cc:     ryazanov.s.a@...il.com, johannes@...solutions.net,
        davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, "Shujun Wang" <wsj20369@....com>
Subject: Re:Re: [PATCH] Fix MRU mismatch issue which may lead to data
 connection lost



At 2022-01-14 23:51:53, "Loic Poulain" <loic.poulain@...aro.org> wrote:
>On Fri, 14 Jan 2022 at 11:07, Slark Xiao <slark_xiao@....com> wrote:
>>
>> In pci_generic.c there is a 'mru_default' in struct mhi_pci_dev_info.
>> This value shall be used for whole mhi if it's given a value for a specific product.
>> But in function mhi_net_rx_refill_work(), it's still using hard code value MHI_DEFAULT_MRU.
>> 'mru_default' shall have higher priority than MHI_DEFAULT_MRU.
>> And after checking, this change could help fix a data connection lost issue.
>
>Interesting, not sure why it fixes data issues, since the device
>should comply with any size.Can you add a Fixes tag then? and add the
>correct [PATCH net] suffix in the subject:
>https://www.kernel.org/doc/html/latest/networking/netdev-FAQ.html
>
>With that:
>
>Reviewed-by: Loic Poulain <loic.poulain@...aro.org>
>
>Thanks,
>Loic
>
Hi Loic,
   Actually, for our Foxconn device SDX55, it has been confirmed that MRU 3500 
would lead to a IPA stuck. IPA stuck would make the data connection lost. 
For other MRU value, like 4000, 4096,32768, we can't reproduce it. 
  We also have report this issue in https://bugzilla.kernel.org/show_bug.cgi?id=215433 .
  I will send a new patch later.

Thanks
Slark
>
>
>
>>
>> Signed-off-by: Shujun Wang <wsj20369@....com>
>> Signed-off-by: Slark Xiao <slark_xiao@....com>
>> ---
>>  drivers/net/wwan/mhi_wwan_mbim.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/wwan/mhi_wwan_mbim.c b/drivers/net/wwan/mhi_wwan_mbim.c
>> index 71bf9b4f769f..6872782e8dd8 100644
>> --- a/drivers/net/wwan/mhi_wwan_mbim.c
>> +++ b/drivers/net/wwan/mhi_wwan_mbim.c
>> @@ -385,13 +385,13 @@ static void mhi_net_rx_refill_work(struct work_struct *work)
>>         int err;
>>
>>         while (!mhi_queue_is_full(mdev, DMA_FROM_DEVICE)) {
>> -               struct sk_buff *skb = alloc_skb(MHI_DEFAULT_MRU, GFP_KERNEL);
>> +               struct sk_buff *skb = alloc_skb(mbim->mru, GFP_KERNEL);
>>
>>                 if (unlikely(!skb))
>>                         break;
>>
>>                 err = mhi_queue_skb(mdev, DMA_FROM_DEVICE, skb,
>> -                                   MHI_DEFAULT_MRU, MHI_EOT);
>> +                                   mbim->mru, MHI_EOT);
>>                 if (unlikely(err)) {
>>                         kfree_skb(skb);
>>                         break;
>> --
>> 2.25.1
>>